Have ibm2668 thinkpad has old pass code can't get in it.

I think this is bios pass? There are two ways - shortcircuiting bios pins or parallel method. Anyway you must disasemble your computer. Try to remove bios battery first (its under keyboard) for two hours. It's a very small chance this will help. When removing battery does nothing, you must search on google which bios pins to shortcircuit in your model. Problem is if you don't have manual/tech scheme for your machine. Try to download it from manufacturer website. You can use a parallel method, but it is harder. Shortcircuiting really works, one guy on fixya was fine with bios pass. Wish to help you more, but I cant, I have the same problem with Fujitsu Siemens, and so on, no solutions, no tech scheme :(
Finally you can use a universal and manufacturer password, search for these two, For universal, you must check what kind and version of bios you have. It usually shows when you just starting computer.